The present application claims priority to Japanese Application No. P11-078192 filed Mar. 23, 1999 which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to a disc-shaped recording medium inspection apparatus and method for inspecting the configuration of the signal recording surface of a disc-shaped recording medium.
2. Description of the Related Art
There has been proposed a disc-shaped recording medium having a signal recording layer to and/or which a signal is written and/or read by a recording/reproducing apparatus. As the disc-shaped recording media, there are already known a magnetic disc to which a magnetic field is applied by a magnetic head having a magnetic gap to write down a magnetic domain corresponding to a signal on a signal recording layer of the magnetic disc, and an optical disc to and/or from which a signal is written and/or read by irradiating thereto a laser light from an optical head of a recording/reproducing apparatus thereto. As the optical discs, there are available a read-only optical disc which has formed on a signal recording layer having a pit and land pattern corresponding to a signal, and a magneto-optical disc and phase-change type optical disc, capable of data write and read.
In the disc-shaped recording medium, a signal is normally written along a recording track formed on the signal recording layer. Specifically, in the above-described read-only optical disc, there are formed pits along the recording track.
For example, the interval between adjacent recording tracks (track pitch, hereinafter) of a conventional CD (Compact Disc) is 1600 nm, and its variation should not be more than 50 nm. On the other hand, the track pitch of a DVD (Digital Versatile Disc) adapted to the high recording density is 740 nm, and thus its variation should not be more than 23 nm or so. That is, as the track pitch is designed smaller in order to enable the high recording density, the configuration of the signal recording surface of the disc-shaped recording medium should be formed with a higher accuracy.
Accordingly, it is required that the inspection apparatus should be able to measure the surface configuration of a disc-shaped recording medium 10 nm or lower. Conventionally, a scanning tunneling microscope (STM) is used as such an inspection apparatus.
However, in case the STM is used to inspect the surface configuration of a disc-shaped recording medium, there is raised a problem that a sufficiently small part of the disc-shaped recording medium under inspection has to be taken by cutting as a sample for inspection by the STM, which however is a destructive inspection.
Also, the STM inspection takes much time. Accordingly, it has been difficult to measure a wide area of the disc-shaped recording medium. Furthermore, a long turnaround time is required, and it has been difficult to effectively feed back the inspection result to the recording process for production of a master disc for example.
It is therefore an object of the present invention to overcome the above-mentioned drawbacks by providing a disc-shaped recording medium inspection apparatus and method, which can inspect the surface configuration of a disc-shaped recording medium accurately, promptly and nondestructively.
According to the present invention, there is provided an apparatus for inspecting the configuration of the signal recording surface of a disc-shaped recording medium. The inspection apparatus includes an imaging means and processing means. The imaging means emits a light having a wavelength falling within a predetermined range for irradiation to the signal recording surface, and detects a return component of the light, reflected from the signal recording surface. The processing means processes an output image from the imaging means. The inspection apparatus inspects the configuration of the signal recording surface based on a result of the output image processing by the processing means.
With the above inspection apparatus according to the present invention, it is possible to eliminate noise included in the output image effectively and promptly by processing the output image from the imaging means by the processing means. It is also possible to nondestructively detect a disc-shaped recording medium since the imaging means irradiates a light to the signal recording surface and detects a return light indicative of the configuration of the signal recording surface.
According to the present invention, there is also provided a method of inspecting the configuration of the signal recording surface of a disc-shaped recording medium. The inspection method includes an imaging step and a processing step. At the imaging step, a light having a wavelength falling within a predetermined range is irradiated to the signal recording surface and a return component of the light, reflected from the signal recording surface, is detected. At the processing step, an output image from the imaging step is processed. The configuration of the signal recording surface is inspected based on a result of the processing at the processing step.
With the above inspection method according to the present invention, it is possible to eliminate noise included in the output image effectively and promptly at the processing step by processing the output image from the imaging step. The inspection method can nondestructively detect a disc-shaped recording medium since a light is irradiated to the signal recording surface and a return light indicative of the configuration of the signal recording surface is detected at the imaging step.
As has been described above, the disc-shaped recording medium inspection apparatus according to the present invention can eliminate noise included in the output image from the imaging means effectively and promptly. Thus, the apparatus measure the configuration of the signal recording surface accurately based on the noise-eliminated output image. Also the inspection apparatus according to the present invention can nondestructively inspect a disc-shaped recording medium since the imaging means irradiates a light to the signal recording surface and detects a return light indicative of the configuration of the signal recording surface. Thus, the inspection apparatus according to the present invention can accurately inspect a disc-shaped recording medium in which the track pitch is small for a high recording density, and effectively feed back the inspection result to the manufacturing process for the disc-shaped recording medium with a reduced turnaround time.
Furthermore, the disc-shaped recording medium inspection method according to the present invention can eliminate noise included in the output image from the imaging step effectively and promptly. Thus, method measure the configuration of the signal recording surface accurately based on the noise-eliminated output image. Also the inspection method according to the present invention can nondestructively inspect a disc-shaped recording medium since a light is irradiated to the signal recording surface and a return light indicative of the configuration of the signal recording surface is detected at the imaging step. Thus, the inspection method according to the present invention can accurately inspect a disc-shaped recording medium in which the track pitch is small for a high recording density, and effectively feed back the inspection result to the manufacturing process for the disc-shaped recording medium with a reduced turnaround time.
These objects and other objects, features and advantages of the present intention will become more apparent from the following detailed description of the preferred embodiments of the present invention when taken in conjunction with the accompanying drawings.